A novel carbon source coated on C-LiFePO<Subscript>4</Subscript> as a cathode material for lithium-ion batteries

The poor electronic conductivity and low lithium-ion diffusion are the two major obstacles to the largely commercial application of LiFePO₄ cathode material in power batteries. In order to improve the defects of LiFePO₄, a novel carbon source polyacrylonitrile (PAN), which would form the hierarchical porous structure after carbonization, is fabricated and used. This work comes up with a simple and facile carbothermal reduction method to prepare porous-carbon-coated LiFePO₄ (C-LiFePO₄-PC) composite and to study the effect of carbon-coated temperature on ameliorating the electrochemical performance. The obtained C-LiFePO₄-PC composite shows a high initial discharge capacity of 164.1 mA h g^?1 at 0.1 C and good cycling stability as well as excellent rate capacity (49.0 mA h g^?1 at 50 C). The most possible factors that improve the electrochemical performance could be related to the enhancement of electronic conductivity and the existence of porous carbon layers. In a word, the C-LiFePO₄-PC material would become an excellent candidate for application in the fields of lithium-ion batteries.     

Influence of γ-ray-induced effects on dielectric dispersion of CuO-doped calcium fluoroborophosphate glass system

γ-Ray-induced dielectric dispersion in CaF₂–B₂O₃–P₂O₅ glasses doped with different concentrations of CuO was investigated. The glass samples were exposed to γ-rays with dose varying within the range 0–10 kGy. The dielectric dispersion and spectroscopic properties were measured before and after γ-ray treatment. Additionally, thermoluminescence studies were performed on post-irradiated glass samples. The results of dielectric properties and dielectric breakdown strength indicated a substantial increase in the insulating strength of CuO containing glasses due to γ-ray irradiation. The analysis of these results together with UV-vis optical absorption, IR spectra, and thermoluminescence studies have indicated a gradual increase in the concentration of mono-valent copper ions due to γ-ray treatment of the glass network. The additional studies have confirmed that these Cu⁺ ions occupy network-forming positions, increase the polymerization of the borophosphate glass network, and facilitates for the increase of insulating strength of the titled glass.     

Generation of Bianchi type V cosmological models with varying Λ-term

Bianchi type V perfect fluid cosmological models are investigated with cosmological term varying with time. Using a generation technique (Camci et al., 2001), it is shown that Einsteins field equations are solvable for any arbitrary cosmic scale function. Solutions for particular forms of cosmic scale functions are also obtained. The cosmological constant is found to be a decreasing function of time, which is supported by results from recent type Ia supernovae observations. Some physical aspects of the models are also discussed.     

Periodic Solutions for Completely Resonant Nonlinear Wave Equations with Dirichlet Boundary Conditions

We consider the nonlinear string equation with Dirichlet boundary conditions u_tt–u_xx=(u), with (u)=u³+O(u⁵) odd and analytic, 0, and we construct small amplitude periodic solutions with frequency for a large Lebesgue measure set of close to 1. This extends previous results where only a zero-measure set of frequencies could be treated (the ones for which no small divisors appear). The proof is based on combining the Lyapunov-Schmidt decomposition, which leads to two separate sets of equations dealing with the resonant and non-resonant Fourier components, respectively the Q and the P equations, with resummation techniques of divergent powers series, allowing us to control the small divisors problem. The main difficulty with respect to the nonlinear wave equations u_tt–u_xx+Mu=(u), M0, is that not only the P equation but also the Q equation is infinite-dimensional.     

Characterization of electrical charge separation at the interface of two aqueous solutions in the presence of concentration gradients and cation/anion mobility ratio asymmetry

Physical consequences of ionic diffusion processes play a major role on the outcome of electrophysiology experiments due to both their contribution to the ionic transmembrane transport and phenomena taking place at the measuring instruments interface. As most of the time heterogenities in biological media with respect to ionic diffusion constants are disregarded, we intended to look upon the general case of ionic diffusion at the interface of two liquids on which gradients of these diffusion constants no longer can be neglected. We developed a theoretical model for the diffusion potential which emerges at an aqueous interface under gradients of concentration and diffusion constants. The experimental validation of our model was achieved through potential difference measurements of the diffusion potential between two solutions containing sodium chloride (NaCl) and glycerine solutions of various concentrations. Within the studied domain of the electrical charge mobility ratio, we noticed that experimental results are in agreement with the theoretically inferred diffusion potential values. This demonstrates that the resulting relationship for the diffusion potential inferred from our model could be applied for other cases, as well. When the ionic solutions contains an indefinite quantity of glycerine or an unknown substance able to modify diffusion constants of sodium and chloride, it was shown that through measurements of the diffusion potential one can infer the unknown concentration of glycerine and the modified ionic mobility ratio. This, in turn, builds up the foundation for a novel yet simple and efficient analitycal sensing device for quantitative determination in the field.     

Resonantly enhanced off-specular X-ray scattering from polymer/polymer interfaces<Superscript>⋆</Superscript>

We have used measurements of the absolute intensity of diffuse X-ray scattering to extract the interfacial tension of a buried polymer/polymer interface. Diffuse scattering was excited by an X-ray standing wave whose phase was adjusted to have a high intensity at the polymer/polymer interface and simultaneously a node at the polymer/air interface. This method permits the capillary-wave-induced roughness of the interface, and hence the interfacial tension, to be measured independently of the polymer/polymer interdiffusion.     

Asymptotic-Preserving Particle-In-Cell method for the Vlasov–Poisson system near quasineutrality

This paper deals with the numerical resolution of the Vlasov–Poisson system in a nearly quasineutral regime by Particle-In-Cell (PIC) methods. In this regime, Classical PIC methods are subject to stability constraints on the time and space steps related to the small Debye length and large plasma frequency. Here, we propose an “Asymptotic-Preserving” PIC scheme which is not subjected to these limitations. Additionally, when the plasma period and Debye length are small compared to the time and space steps, this method provides a consistent PIC discretization of the quasineutral Vlasov equation. We perform several one-dimensional numerical experiments which provide a solid validation of the method and its underlying concepts, and compare the method with Classical PIC and Direct-Implicit methods.